Support passing a custom coverage formatter to finalizeCoverage() (#5208)

packages/flutter_tools/lib/src/test/coverage_collector.dart

@@ -58,16 +58,18 @@ class CoverageCollector {
   List<Future<Null>> _jobs = <Future<Null>>[];
   Map<String, dynamic> _globalHitmap;
 
-  Future<String> finalizeCoverage() async {
+  Future<String> finalizeCoverage({Formatter formatter}) async {
     assert(enabled);
     await finishPendingJobs();
     printTrace('formating coverage data');
     if (_globalHitmap == null)
       return null;
-    Resolver resolver = new Resolver(packagesPath: PackageMap.globalPackagesPath);
-    LcovFormatter formater = new LcovFormatter(resolver);
-    String packagePath = Directory.current.path;
-    List<String> reportOn = <String>[path.join(packagePath, 'lib')];
-    return await formater.format(_globalHitmap, reportOn: reportOn, basePath: packagePath);
+    if (formatter == null) {
+      Resolver resolver = new Resolver(packagesPath: PackageMap.globalPackagesPath);
+      String packagePath = Directory.current.path;
+      List<String> reportOn = <String>[path.join(packagePath, 'lib')];
+      formatter = new LcovFormatter(resolver, reportOn: reportOn, basePath: packagePath);
+    }
+    return await formatter.format(_globalHitmap);
   }
 }

packages/flutter_tools/pubspec.yaml

@@ -10,7 +10,7 @@ environment:
 dependencies:
   archive: ^1.0.20
   args: ^0.13.4
-  coverage: ^0.7.9
+  coverage: ^0.8.0
   crypto: '>=1.1.1 <3.0.0'
   file: ^0.1.0
   http: ^0.11.3